"The witnesses we have saw her (Sarah) once she started screaming so we are certainly trying to piece things together," he told Sydney radio 2UE.

"I can't confirm for you that there were teenage girls running away; there certainly are a number of reports of some teenagers seen leaving the park and our interest is obviously in relation to those people.

"There's some talk about masks being worn and that's why we're having difficulty working out the sex of the teenagers, but we're certainly very interested in them.

The family was taking the accident "very tough", he said.

"They're very shaken, I worry about the little siblings who saw this matter."

The girl's siblings, aged five and seven, would be counselled today, he said.

"We're organising some specialised counselling for them today and its very nasty sort of stuff."

Macquarie Fields Local Area Commander, Superintendent Mark Rattenbury, said Sarah had been in the park with her two siblings and mother.

"The other two (siblings) had only just entered the park with Sarah and they had run forward to the swings and the slippery dip as young people do and Sarah was more or less isolated then, but only a short distance away," Supt Rattenbury told Sydney radio 2GB.

"The mother, or step mother, was some short distance behind that with one of the other siblings."

"We're not clear on what has taken effect after that."

Insp Appleton said the park in which the incident took place was just an "average little reserve next to a child care centre".

"It (was) mid afternoon, people were around, it's suburbia, nothing outstanding to it at all."